This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Chronic lower back pain (CLBP) affects millions of people and cost billions of dollars per year in the United States alone. Recent evidence indicates that chronic back pain may cause structural changes in brain gray matter (GM), suggesting that GM changes may be an important metric in evaluating the efficacy of pain treatments. In this double-blind crossover study, we used tensor based morphometry (TBM) to test our hypothesis that treatment with duloxetine (a specific serotonin-norepinephrine reuptake inhibitor) would cause GM changes that are distinct from those caused by treatment with placebo. 14 male subjects with CLBP were recruited. They rated pain as at least 4/10 on average for the two weeks prior to the start of the study and were not on pain medications. Study design was a double blind, placebo control, 12 week crossover study utilizing duloxetine as the active drug. Structural scans were conducted at baseline and at the end of each drug period. To read about other projects ongoing at the Lucas Center, please visit http://rsl.stanford.edu/ (Lucas Annual Report and ISMRM 2011 Abstracts)